Pollution assessment, distribution and sources of PAHs in agricultural soils of Pearl River Delta - The biggest manufacturing base in China

A large scale of soil survey was performed to determine the contents, distributions and sources of 16 polycyclic aromatic hydrocarbons (PAHs) in 231 agricultural soils under 3 land-use types from 5 regions of the subtropical Pearl River Delta (PRD). The average sum of 16 PAHs in all soil samples is 316.5 mu g center dot kg(-1), with range from ND to 4079 mu g center dot kg(-1). Three- and 4-ring PAHs are the most abundant PAHs that contribute to 73.0% of total contents. The most abundant components are phenanthrene, benzo(b)fluoranthene and fluoranthene. ANOVA and principal component analyses (PCA) indicate that soil samples from Dongguan and Zhongshan contain greater PAHs than other regions. More abundant carcinogenic and higher molecular weight PAHs accumulated in soils from Dongguan and Zhongshan, while higher low molecular weight PAHs were in soils from Guanghzou, Huizhou and Shunde. Soil PAHs from 3 land uses are not statistically different. Additionally, 5 PAH compound ratios suggest that soil PAHs in PRD derived from mixture of pyrogenic and petrogenic sources, but the majorities are pyrogenic sources. PAHs were further identified as mixture of petroleum combustion and grass, wood, and coal combustion. Some soil PAHs were revealed vehicle emission, coal soot and petroleum sources. The 5 regions showed different PAHs sources according to some compound ratios, but no marked distinction between regions from 2 banks of the Pearl River because of major wind direction, distribution of riverway and industry.